PROTECTION AND POLYMERIZATION OF FUNCTIONAL MONOMERS .17. SYNTHESIS OF WELL-DEFINED POLY(VINYLACETOPHENONE)S BY MEANS OF ANIONIC LIVING POLYMERIZATION OF TERT-BUTYLDIMETHYLSILYL ENOL ETHERS OF VINYLACETOPHENONES

The anionic polymerizations of the trimethylsilyl enol ether of 4-vinylacetophenone (1), the tert-butyldimethylsilyl enol ethers of 4-, 3-, and 2-vinylacetophenones (2a-c), the tert-butyldimethylsilyl enol ether of 4-vinylpropiophenone (3), and the tert-butyldimethylsilyl enol ethers of 4-(2-propenyl)acetophenone (4), and 4-(2-propenyl)propiophenone (5) were carried out in THF at -78-degrees-C with a variety of anionic initiators. Among the monomers, 2a, 2b, 3, 4, and 5 underwent anionic living polymerization to afford quantitatively polymers of predictable molecular weights from [monomer] to [initiator] ratios and narrow molecular weight distributions. Novel well-defined triblock copolymers of both ABA and BAB types were also synthesized by sequential polymerizations of 2a or 2b and styrene and vice versa. On the contrary, attempts to anionically polymerize 1 and 2c failed under the same conditions. Complete deprotection of the tert-butyldimethylsilyl groups of poly(2a) and poly(2b) to poly(vinylacetophenone)s was achieved by treatment with either 0.5 N HCl or (C4H9)4NF. The resulting poly(vinylacetophenone)s were found to possess narrow molecular weight distributions, almost identical to those of the parent poly(2a) and poly(2b).